BOGE UJ VS. TENDON VS. CARDAN – WHAT ARE THE BEST TYPES OF UNIVERSAL JOINT FOR WINDSURFING?
There are three main varieties of Universal Joint – or ‘UJ’ – used in windsurfing. These are attached to baseplates that fix the rig (mast, boom and sail) to the board and allow multi-directional movement when the mast falls and when the rig is being used in dynamic motion for steering and manoeuvres when sailing.
Which type to choose depends on the kind of sailing you mainly do, for example, racing, freeriding, wave sailing etc.
Here’s a summary of the different varieties generally available on the market.
BOGE JOINT (OR POWER JOINT)
This is the classic ‘hourglass’ UJ and most commonly used style. It’s also the most impact-resistant pick, but offers less sideways resistance and stiffness.
The flexible nature of the Boge UJ is more forgiving in bumps and lumps with a ‘suspension-like’ nature that absorbs hard landings and smooths out the effects of sailing across chop.
In general, Boge joints also have a longer lifespan than tendon joints.
All UJs need a regular inspection for wear and tear.
To check the condition, flex the joint sideways towards the baseplate a few times, rotating around each side of the UJ and look for flaws such as stretch marks or cracks.
To replace a Boge or power joint (where the glue holding the pin into the rubber is very strong), you will need a heat gun (perhaps a hair dryer will do the job too!) as the resin will only release over a certain temperature before undoing the parts and replacing them.
Always use 'loctite is similar epoxy resin 'superglue' to ensure a secure connection.
Best For: Bump ‘n Jump/high-wind freeriding/heavy-weather wavesailing.
The tendon offers the sturdiest transmission between board and rig with the least susceptibility to sideways movement and deflection.
This direct type of connection is preferred by those that like instant feedback from the board through their hands and a feel of ‘precision’ in handling.
Although they have less ‘suspension' effect in choppy sea states, tendons can also offer added control as they are slightly shorter and lower the sail’s Centre of Effort (COE) close to the deck, which can be useful for speed or slalom racing, especially in overpowered, rough-water conditions. (A lower COE can also benefit shorter riders.)
However, on super small speed 'needles' (50-cm. wide or less), some sailors prefer a Boge joint as it can be easier to waterstart in open water with a more flexible UJ that prevents the board from being stuck in a 'bottom down' position.
Tendons also need regular safety inspections. Tendons can also be easier to replace with basic tools. However, to do this you must partially dismantle them.
Failure usually occurs around the hole at the top or bottom where the horizontal pins holding them in place run through.
When replacing a tendon, make sure the tendon fits perfectly into the base plate and top part.
Also make sure that both ends of the tendon are fully supported. If they are not, the forces will focus only on the tendon material around the hole and wear very fast.
To test this, insert the tendon first without any mounting parts. Rotate and push the tendon firmly until the holes in base and top are in line.
Alignment height differences larger than 1 mm require a washer ring made from any hard material (non corrosive metal or hard plastic).
Best For: Racing/speed/performance wavesailing in smooth water/rough water control and lowering COE.
These 'links connecting the top and bottom of a Cardan connection offer little absorption properties, which means they are not the most suitable for accomplished riders.
However the light feeling they provide is popular with beginners and improvers, mostly at schools and rental centres.
Best for beginners and improvers on flat water